Analytical determination of orthophosphate in water

Methods for orthophosphate determination and the problems of interferences are reviewed.An important group of methods utilizes the phosphomolybdate complex. The complexation step, the reduction step and the extraction step are treated separately and alternative procedures compared.Another group of methods uses ion association complexes; they are primarily used in physiology and not commonly used in water analyses today.Enzymatic methods for orthophosphate analysis in natural waters have been developed lately and are ready for application in selected waterbodies.Flame spectroscopic, fluorometric, gas chromatographic, ion exclusion chromatographic, inductively coupled plasma and other methods are also shortly presented.Radiobiological bioassays for orthophosphate are also available.In conclusion it was emphasized that the most common and reliable technique still is the molybdenum blue method as modified by Murphy & Riley (1962).The need for more specific and sensitive methods is particularly strong in investigations of phosphorus turnover and phosphorus limitation in natural waters. For these purposes the enzymatic phosphatase methods has advantages due to their specificity for orthophosphate and they might offer an alternative to the molybdenum blue method.